This is a multi-institutional study with data analyses being handled by the site at the University of North Carolina. All data have been collected, but the analyses are not yet completed. It has already been determined that there is a 10% prevalence of nontuberculous mycobacteria in sputum from patients with cystic fibrosis and that approximately 2% appear to be continuously colonized. The major aim of this study was to determine whether mycobacterial colonization effected clinical outcome. Data analysis addressing this point is now underway but the results are not yet available.